1. Field of the Invention
The present invention relates to a spindle motor for rotating a recording disk such as a magnetic disk.
2. Description of the Related Art
In general, a spindle motor includes a shaft member, a hub member rotatably mounted on the shaft member with a bearing member therebetween, a rotor magnet mounted on the hub member, and a stator disposed in opposed relation to the rotor magnet. A recording disk is mounted on the hub member in a predetermined manner. A magnetic fluid sealing means is provided on an outer side of the bearing means in order to prevent impurities, such as grease for the bearing member, from entering a disk chamber. The magnetic fluid sealing means includes a magnetic fluid for forming a sealing layer, and a magnetic fluid retaining means for magnetically retaining the magnetic fluid.
In the above-described type of spindle motor, a magnetic flux from the magnetic fluid retaining means leaks, and adversely affects a recording member mounted on the hub member and/or a head means for reading (and/or writing) information. Such leaking magnetic flux has become a subject of attention as the information recording density increases.
In the spindle motor of the above-described type, a flexible substrate is generally used for supplying a driving current to a coil of the stator in a predetermined manner. That is, the coil is electrically connected to a terminal portion provided on one end portion of the flexible substrate, and a connector member provided on the other end portion of the flexible substrate is electrically connected to a connector means of a driving device. Consequently, electrical connection of the flexible substrate is completed, and the size of the motor is increased.
Furthermore, in the aforementioned type of spindle motor, an internally threaded hole is formed in the shaft member, and a clamp member for mounting a recording disk is mounted by bringing an attaching screw into engagement with this internally threaded hole. However, the internally threaded hole extends only halfway through the shaft member. Therefore, when the shaft member (or both the hub member and the shaft member when the shaft member is formed integrally with the hub member) is surface processed, a surface processing liquid may not enter the distal end portion of the internally threaded hole, leaving the distal end of the internally threaded hole in a non-processed state.